Now, while re-watching the latest episode, I noticed this:

http://i.imgur.com/DmidaMp.png

When PJ asked the suspects to show their left shoulders, McAllister looked at his hat for a brief moment, then glanced away. That scene was not consistent with the scenes before and after. Go back to the episode and re-watch that scene. Is it possible that the bomb was under his hat?

Now regarding the promo of the next episode. What is the bigger lie? Is it the death of partridge?